Merge remote-tracking branch 'upstream/master' into errors-phase-2

.gitignore

doc/manual/command-ref/opt-common-syn.xml

doc/manual/command-ref/opt-common.xml

mk/libraries.mk

perl/lib/Nix/Store.xs

src/libexpr/primops/fetchTree.cc

src/libfetchers/fetchers.cc

src/libfetchers/tarball.cc

src/libmain/common-args.cc

src/libmain/loggers.cc

src/libmain/loggers.hh

src/libmain/progress-bar.cc

src/libmain/progress-bar.hh

src/libmain/shared.cc

src/libstore/build.cc

src/libstore/daemon.cc

src/libstore/export-import.cc

src/libstore/globals.hh

src/libstore/local-store.cc

src/libstore/names.cc